The present invention relates generally to improvements in electronic devices or components and it relates more particularly to an improved hermetically sealed semiconductor device such as a photoconductive element or the like.
There has been heretofore proposed a photoconductive device of a construction which, as shown in FIG. 1 in the drawings herein, includes a photoconductive film 2 deposited on a substrate 1 by conventional or known coating or vacuum evaporating processes and spaced electrodes disposed thereon. The so fabricated body is shielded from the ambient atmosphere by means of a hermetic case 6, the hermetic case containing an inert gas or dry air therein. The reason why a photoconductor layer should be shielded from the atmosphere is that the photoconductor layer, prepared as above, by the employment of a coating or a vacuum evaporating process, as well as the electrodes are susceptible to to the influence of moisture, oxygen, oil and the like. Although the aforesaid hermetic shielding construction is satisfactory in shielding such a fabricated body from the atmosphere, by the use of a metal and glass, the glass is particularly susceptible to breakage due to heat and external forces, particularly an impact force. Thus, when a crack in the glass occurs, then air enters the interior of the case from outside, thereby lowering and adversely effecting the characteristics of the photoconductive element. Another attempt to provide a photoconductive element is such that a synthetic resin such as epoxy, urethane, or vinyl resin and the like is formed on the surface of a photoconductive film by means of a coating or a molding process. This latter procedure is simple in practice and well adapted for use in mass production, as compared with the sealing process using a hermetic case. In addition, the absence of the use of glass provides mechanical stability. However, the synthetic resin itself suffers from a deficiency in humidity resistance. In other words, active gasses such as moisture and oxygen tend to enter the interior through pinholes or cracks caused in the resin cover due to heat impact, thus failing to afford a construction which provides complete or adequate sealing. It is thus clear from the above, that the hermetically sealed electronic members heretofore proposed or available leave much to be desired.